Optical feedback RF ablator and ablator tip

ABSTRACT

An ablation catheter comprises an elongated catheter body; at least one ablation element disposed in a distal portion which is adjacent the distal end of the catheter body; an illumination optical element disposed in the distal portion, the illumination optical element being light-transmissive to emit light from the illumination optical element to the targeted tissue region; and a collection optical element disposed in the distal portion, the collection optical element being light-transmissive to collect one or more of returned, backscattered or newly excited light from the targeted tissue region. The illumination or excitation optical element and the collection optical element are axially spaced from one another and axially optically isolated from one another within the distal portion to substantially prevent light from traveling between the illumination optical element and the collection optical element along a path within the distal portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.14/640,105, filed 6 Mar. 2015 (“the '105 application”), now pending,which is a continuation of U.S. application Ser. No. 13/085,789, filed13 Apr. 2011 (“the '789 application”), now U.S. Pat. No. 8,986,292. The'105 and '789 applications are hereby incorporated by reference asthough fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates generally to ablation devices and, morespecifically, to optical feedback radiofrequency (RF) ablators andablator tips.

Proposed optical-feedback catheters such as those of Biosense-Webstermainly employ an RF catheter in which the thermally ablative RF tip isalso capable of the optical detection of the thermal lesions the RF tipforms. See, e.g., US2008/0119694, which is incorporated herein byreference in its entirety. The thermally ablative RF tip has a hollow RFelectrode and the outer RF electrode surface is electrically conductingand therefore can deliver RF ablation by electrical contact to targettissue. Inside the hollow metal-coated or metal-walled RF tip electrodeare two radially isolated optical elements or chambers, each of which isconnected to a separate optical fiber running along the catheter lumento the proximal catheter handle. The first fiber delivers opticallybroadband illumination light to the first tip optical cavity (theemission cavity) from which the light emits into nearby tissue through anumber of optical vias bridging the tissue and the emission opticalelement. Thus the emission optical element acts to omni-directionallyspray or distribute emanating broadband excitation light from thenumerous optical emission vias into the contacting tissue. Note that theomni-directional 360 degree optical output assures that tissue whichcontacts only one side face of the tip (which is typical) will beilluminated without requiring axial tip rotation. A second opticallyisolated element in the RF tip is the optical reception element. It isoptically coupled to the tissue by a second separate set of interspersedoptical vias which receive backscattered light from tissues (i.e.,received light which comprises incoming backscattered illuminationlight). The optical reception element is coupled to the second opticalfiber which is used to route incoming backscattered light from the tipback to the catheter handle and to an optical sensor such as an opticalspectrometer. The received or backscattered light spectrum iswavelength-scanned by the spectrometer looking for amplitude changes atvarious wavelengths particularly those corresponding to changing opticalabsorption or scattering mechanisms in the tissue. Thus, for example,thermal ablation lesions reduce water content in tissue so that opticalreflectance or backscattering is affected at one or more wavelengthssensitive to water content. Optical spectroscopy has been used for realtime assessment of RF cardiac tissue ablation. See Stavros G. Demos &Shiva Shararch, “Real Time Assessment of RF Cardiac Tissue Ablation withOptical Spectroscopy,” Optics Express, Vol. 16, No. 19 (Sep. 15, 2008),which is incorporated herein by reference in its entirety. Note that RFablations are usually done on target tissue either contacting the sideof the RF tip or contacting the end (forward looking end) of the RF tip.Thus most preferably, by omni-directional performance, is meant opticallesion detection of RF lesions both radially (sideways at any rotationalangle between 0 and 360 degrees) and forwardly such as with the tipsitting roughly perpendicular to the tissue target or at a tilted anglethereto such as between 0 and 60 degrees.

It has been considered advantageous if not required to optically isolatethe two optical elements and their respective sets of optical vias. Theargument for this is so as not to saturate the optical receiver (thewavelength spectrometer) with ingoing light which would otherwise travelwithin the tip directly from the emission fiber to the collection fiberwithout ever having been emitted from the tip and tissue-scattered. Inorder to optically isolate the two elements and their respective viasets yet still have omni-directional emanation and reception, the tip isconfigured to have the emission element within the reception element andit is isolated from it by a radial opaque wall or film. Thus theemission vias, although they pass through the outer reception element,do not dump light directly into the reception element. The receptionelement vias pass light into the outer annular reception element so thatthey never penetrate the interior emission element. This arrangementtotally isolates the outgoing and incoming optical paths so thatreception signal/noise ratio is maximal per such an argument.

A significant drawback of that double walled optical element tip designand interspersed yet isolated optical via sets is that it is very hardto make in terms of difficulty and manufacturing yield and typicallyrequires a double shell structure wherein penetrating optical vias mustall be each individually optically isolated. Another problem is that thecumulative area of the emanation optical vias and the cumulative area ofthe reception optical vias are each quite small; otherwise, the metalshell has too many holes in it to be mechanically sound. The prior artproposed designs such as this also make it difficult to provide a salineirrigated (cooled) RF electrode unless irrigation flow paths double asoptical paths. This is considered a limit on the number and scope ofpossible product designs and not necessarily a technical issue.

BRIEF SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, an ablationcatheter comprises an elongated catheter body extending longitudinallybetween a proximal end and a distal end along a longitudinal axis; andat least one ablation element disposed in a distal portion which isadjacent the distal end of the catheter body to ablate a targeted tissueregion outside the catheter body; an illumination or excitation opticalelement disposed adjacent the at least one ablation element, theillumination optical element being light-transmissive to emit light fromthe illumination optical element to the targeted tissue region; and acollection optical element disposed adjacent the at least one ablationelement, the collection optical element being light-transmissive tocollect one or more of returned, backscattered or newly excited lightfrom the targeted tissue region in response to the light emitted fromthe illumination or excitation optical element to the targeted tissueregion. The illumination or excitation optical element and thecollection optical element are axially spaced from one another andaxially optically isolated from one another within the distal portion tosubstantially prevent light from traveling between the illuminationoptical element and the collection optical element along a path withinthe distal portion.

In some embodiments, an opaque member is disposed in the catheter bodybetween the illumination optical element and the collection opticalelement to axially optically isolate the illumination optical elementfrom the collection optical element. The ablation catheter furthercomprises a first optical fiber in communication with the illuminationoptical element; and a second optical fiber in communication with thecollection optical element. The first optical fiber is opticallyisolated from the collection optical element and the second opticalfiber is optically isolated from the illumination optical element. Oneor more of the illumination optical element or collection opticalelement each comprise a substantially annular optical element. The atleast one ablation element comprises a metallic shell which at leastpartially covers the illumination optical element and the collectionoptical element; and the metallic shell includes a plurality of firstopenings through which to emit light from the illumination opticalelement to the targeted tissue region and a plurality of second openingsthrough which to collect, by the collection optical element, light fromthe targeted tissue region in response to the light emitted from theillumination optical element to the targeted tissue region. Theillumination optical element has one or more interior surfaces coveredby opaque light-blocking layers; and the collection optical element hasone or more interior surfaces covered by opaque light-blocking layers.

In specific embodiments, at least one of the illumination opticalelements emits light or the collection elements receives light, along atleast one path, oriented at an angle of between about 90 degrees andzero degrees relative to the longitudinal axis. The illumination opticalelement includes a plurality of illumination optical vias oriented at anangle relative to the longitudinal axis but having a directionalcomponent along the longitudinal axis toward the collection opticalelement; and the collection optical element includes a plurality ofcollection optical vias oriented at an angle relative to thelongitudinal axis but having a directional component along thelongitudinal axis toward the illumination optical element. At least oneof the illumination or collection optical vias comprises a light conduitfor light to travel through, the light conduit including, at least inpart, a material selected from the group consisting of liquid, polymer,glass, transparent material, and translucent material. The illuminationoptical element includes an illumination annular lens to direct light atan angle relative to the longitudinal axis but having a directionalcomponent along the longitudinal axis toward the collection opticalelement; and the collection optical element includes a collectionannular lens to receive light at an angle relative to the longitudinalaxis but having a directional component along the longitudinal axistoward the illumination optical element.

In some embodiments, the at least one ablation element includes aside-ablating element disposed between the illumination optical elementand the collection optical element. The at least one ablation elementcomprises a first ablation element which is axially situated at an axialdistance equal to or greater than zero from the illumination opticalelement and an axial distance equal to or greater than zero from thecollection optical element. An ablation element includes ametal-containing, electrically conductive electrode material. The atleast one ablation element includes a forward ablation element disposedat the distal end and adjacent the collection optical element. Theforward ablation element comprises a metal-containing solid memberhaving a rounded atraumatic shape. The ablation catheter furthercomprises a light conduit running axially inside the distal portion, thelight conduit for at least one of delivering emitted light to theillumination optical element or receiving returned light from thecollection optical element. The ablation catheter further comprises afirst optical fiber in communication with the illumination opticalelement; and a second optical fiber in communication with the collectionoptical element. The first optical fiber is substantially opticallyisolated from the collection optical element and the second opticalfiber is substantially optically isolated from the illumination opticalelement. The illumination optical element includes an externalillumination annular surface oriented at an angle relative to thelongitudinal axis but having a directional component along thelongitudinal axis toward the collection optical element; and thecollection optical element includes an external collection annularsurface having a convex profile, the convex profile including a rearwardportion oriented at an angle relative to the longitudinal axis buthaving a directional component along the longitudinal axis toward theillumination optical element and a forward portion oriented at an anglerelative to the longitudinal axis but having a directional componentalong the longitudinal axis toward the distal light transmissionopening.

In specific embodiments, the light transmission element has a hollowinterior, and the ablation catheter further comprises at least oneirrigation fluid channel coupled with the hollow interior of the lighttransmission element and being in thermal communication with the distalportion of the catheter body. At least a portion of one of theillumination optical element or the collection optical element isliquid-permeable. The illumination optical element is annular and thecollection optical element is annular, and the illumination opticalelement is axially spaced from the collection optical element. Theillumination optical element is coupled to a light source to emit lightsideways to the targeted tissue region; and the collection opticalelement is configured to receive sideways the returned, backscattered ornewly excited light from the targeted tissue region in response to thelight emitted sideways from the illumination optical element. Oneelement of the illumination optical element or the collection opticalelement is annular and oriented sideways at an angle relative to thelongitudinal axis but having a directional component along thelongitudinal axis toward the distal end, and the other element of theillumination optical element or the collection optical element isoriented in a forward direction toward the distal end and disposeddistally with respect to the one element.

In accordance with another aspect of the invention, an ablation cathetercomprises an elongated catheter body extending longitudinally between aproximal end and a distal end along a longitudinal axis; at least oneablation element disposed in a distal portion which is adjacent thedistal end of the catheter body to ablate a targeted tissue regionoutside the catheter body; an illumination or excitation optical elementdisposed in the distal portion, the illumination optical element beinglight-transmissive to emit light from the illumination optical elementto the targeted tissue region; and a collection optical element disposedin the distal portion, the collection optical element beinglight-transmissive to collect one or more of returned, backscattered ornewly excited light from the targeted tissue region in response to thelight emitted from the illumination or excitation optical element to thetargeted tissue region. The illumination or excitation optical elementand the collection optical element are axially spaced from one anotherand axially optically isolated from one another within the distalportion to substantially prevent light from traveling between theillumination optical element and the collection optical element along apath within the distal portion.

In some embodiments, the at least one ablation element is adjacent atleast one of the illumination optical element or the collection opticalelement. The at least one ablation element comprises a metallic filmwhich at least partially covers at least one of the illumination opticalelement or the collection optical element, the metallic film beingsubstantially transparent optically and electrically conductive. The atleast one ablation element further comprises a metal-containing blockdisposed between the illumination optical element and the collectionoptical element, the metal-containing block being electrically coupledto the metallic film. The at least one ablation element comprises ametallic shell which at least partially covers at least one of theillumination optical element or the collection optical element; and themetallic shell includes a plurality of first openings through which toemit light from the illumination optical element to the targeted tissueregion and a plurality of second openings through which to collect, bythe collection optical element, light from the targeted tissue region inresponse to the light emitted from the illumination optical element tothe targeted tissue region. The at least one ablation element comprisesa metallic shell which at least partially covers the illuminationoptical element but not the collection optical element. The at least oneablation element comprises a metal-containing block disposed between theillumination optical element and the collection optical element.

These and other features and advantages of the present invention willbecome apparent to those of ordinary skill in the art in view of thefollowing detailed description of the specific embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1E are sectional views illustrating a simple method of making acombination RF ablating and optical sensing tip having a single opticaltip element for an optical feedback RF ablator which has a metallicshell.

FIG. 2A is a sectional view of an optical feedback RF ablatorillustrating a time-gated pitch-catch approach wherein emitted light ispulsed and turned off before received light is collected.

FIG. 2B is a sectional view of an optical feedback RF ablatorillustrating a two fiber two optical-element scenario using constantillumination.

FIG. 2C is a sectional view of an optical feedback RF ablatorillustrating the use of metallic thin films overlying optical elements.

FIG. 2D illustrates lesion formation for an optical feedback RF ablatorhaving a similar arrangement of optical and ablator elements as in FIG.2B.

FIG. 2E illustrates lesion formation for an optical feedback RF ablatorhaving an optical receiver separated from the ablation shell and servingonly an optical receive function.

FIG. 2F illustrates lesion formation for an optical feedback RF ablatorin which both optical transmitter and receiver are separated from theablation shell as separate isolated transmitter and receiver.

FIG. 3 schematically illustrates an optical feedback RF ablator withside-looking optical feedback.

FIG. 4 schematically illustrates an optical feedback RF ablator withside-looking and forward-looking optical feedback.

FIG. 5 schematically illustrates an optical feedback RF ablator withside-looking and forward-looking optical feedback and enhanced optics.

FIGS. 6A and 6B illustrate the optical transmit or emission elementportion of FIG. 5.

FIG. 7 schematically illustrates an optical feedback RF ablator withside-looking and forward-looking optical feedback utilizing tip-mountedlight source(s).

FIG. 8 is a schematic diagram of an apparatus for RF ablation withoptical feedback.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the invention, reference ismade to the accompanying drawings which form a part of the disclosure,and in which are shown by way of illustration, and not of limitation,exemplary embodiments by which the invention may be practiced. In thedrawings, like numerals describe substantially similar componentsthroughout the several views. Further, it should be noted that while thedetailed description provides various exemplary embodiments, asdescribed below and as illustrated in the drawings, the presentinvention is not limited to the embodiments described and illustratedherein, but can extend to other embodiments, as would be known or aswould become known to those skilled in the art. Reference in thespecification to “one embodiment,” “this embodiment,” or “theseembodiments” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention, and the appearances ofthese phrases in various places in the specification are not necessarilyall referring to the same embodiment. Additionally, in the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present invention. However,it will be apparent to one of ordinary skill in the art that thesespecific details may not all be needed to practice the presentinvention. In other circumstances, well-known structures, materials,circuits, processes and interfaces have not been described in detail,and/or may be illustrated in block diagram form, so as to notunnecessarily obscure the present invention.

In the following description, relative orientation and placementterminology, such as the terms horizontal, vertical, left, right, topand bottom, is used. It will be appreciated that these terms refer torelative directions and placement in a two dimensional layout withrespect to a given orientation of the layout. For a differentorientation of the layout, different relative orientation and placementterms may be used to describe the same objects or operations.

Exemplary embodiments of the invention, as will be described in greaterdetail below, provide optical feedback RF ablators and ablator tips.

FIGS. 1A-1E are sectional views illustrating a simple method of making acombination RF ablating and optical sensing tip having a single opticaltip chamber or element for an optical feedback RF ablator which has ametallic shell. The same optical element carries emission and receptionlight; whether that emission and reception is done simultaneously orsequentially depends on the inventive embodiment.

FIG. 1A shows a plug 1 which may be a hot-pressed moldable glass plug ofdiameter D and length L. The plug 1 has a dome-shaped end and anotherwise cylindrical body in the embodiment shown. The glass in theglass plug 1 is substantially transmissive of the optical wavelengths ofinterest. Typically these wavelengths at least include some infraredwavelengths to garner maximal tissue penetration. The plug 1 isfinish-molded or hot-pressed to final dimension and surface finish as itcan be such as by using Sumitomo® moldable lens glass materials in apolished mold. This is referred to as a standalone plug component. Asused herein, a plug or a tip plug is a member to be placed in or formedinside of an RF ablating shell whose function is to route light andirrigation fluid (e.g. saline) including being capable of mating tolight fibers or conduits and fluid delivery lumens as necessary. Theplug material will preferably, at least in some plug portions, beinherently light-transmissive (i.e., such as clear and transparent,translucent, or diffusely transmissive and scattering). Inherentlyoptically transmissive materials include glasses and polymericmaterials, both in solid and porous or permeable form. The porosity orpermeability, if present, may be saline or liquid/gel saturated duringuse and might serve as one or both of saline or cooling flow pathsand/or localized optical conduits.

FIG. 1B shows an RF power delivering metallic shell 2 of thickness W.This thickness W is measured in mils or thousandths of an inch such asabout 0.001 inches to about 0.025 inches, more preferably about 0.003inches to about 0.015 inches, most preferably about 0.007 to about 0.012inches. This metallic or metal-containing shell 2 may be, for example,made via deep drawing metal or by metal electroforming onto a mandrel.The purpose of the shell 2 is to provide most or all of the electricaland thermal conductivity needed by such an RF ablative tip as well as toprovide a metallic tip with familiar tissue electrical-contact orelectrical work-function properties. In a first specific embodiment, theshell 2 is copper-containing or copper-alloy containing, deep drawn toshape, and over plated/coated with a bilayer such as gold on nickel orplatinum on chrome. In a second embodiment the shell 2 is formed byelectroforming a metallic shell 2 out of electrodeposited copper ornickel directly onto the glass or polymer plug 1. In that case the glassor polymer plug 1 acts as the electroforming mandrel. As before anovercoat of noble metal such as widely employed platinum orplatinum-iridium (or possibly gold or rhodium) could be plated ordeposited thereon with an underlying adhesion metal. The construction ofthe plug 1 and shell 2 forming the tip must assure that during thermalcycling caused by RF ablation differential, thermal expansion of theshell and plug does not cause the plug-shell interface bond to fail intension or shear. Thus if a low expansion glass plug is used, one maywant to use electroformed nickel or deep-drawn Invar® or other lowexpansion metal for the tip shell with an accompanying noble metalovercoat. If an optical epoxy or polymer is used for the plug materialwhich typically has high thermal expansion, then it is preferably pairedwith a high expansion shell material such as electroformed copper or adeep-drawn copper alloy. As used herein, a shell or a tip shell isformed of an electrically and thermally conducting metal, metal alloy,metal laminate, metal composite, metal impregnated ceramic, metalimpregnated glass, or cermet, either as a standalone component or as abuilt-up deposit on a mandrel or form, the mandrel or form possiblybeing disposed of as a disposable after use or being the permanent tipplug. We also note that in the case of a polymeric or epoxy plug, anelectroformed or deep-drawn shell can serve as a casting mold for such acast plug polymer.

FIG. 1C shows the glass plug 1 and the metallic shell 2 assembled into asubassembly 3. There are various available methods including a number ofpreferred methods of forming the subassembly 3. According to one method,a preformed standalone plug 1 is epoxy-bonded or cemented into the shell2 using an optically clear epoxy with an index of refraction allowingfor good transmission of the outgoing and ingoing light. In anotherapproach, a plug 1 is thermally molded or cast into the metal shell 2(using the shell as a casting container or mold), preferably such thatan optically transparent bonded plug/shell interface is obtained. In yetanother method, the shell 2 is electroformed or plated directly upon aglass or polymeric preformed plug 1. We note that electroforming isactually a form of high-rate plating wherein very thick (mils or more)platings (structural deposits) are desired.

FIG. 1D shows a subassembly 4 which is similar to that of FIG. 1C butthe subassembly 4 further includes a pair of laser-drilled optical vias5 through the metal shell 2′ and into the underlying plug 1′. It shouldbe noted that after laser-drilling, one may backfill the laser holeswith an optical epoxy or with reflowed plug glass. In that manner thereis excellent optical coupling from the tissue all the way some distanceinto the plug 1′ along the drilled and filled optical conduit.Furthermore, the optical vias 5 may be arranged to emit light and/or togather returned or backscattered light. For this embodiment, the plugcan be formed by casting or molding it into a shell that already has theoptical vias formed therein, and the plug casting or molding processwill serve also to fill the shell portion of the vias with the cast ormolded optically transmissive material if it is desired to fill thevias. In specific embodiments, multiple optical vias are distributedabout the tip surface (around the longitudinal axis of the catheter tip)such that substantially 360 degree radial omni-directional sensing oflesions is rendered possible. Preferably, forward-looking optical vias(not shown in FIG. 1) are also utilized such that tip-end lesions can bemonitored as well as tip-side lesions.

FIG. 1E shows a subassembly 4A which again is similar to that of FIG.1C, but the subassembly 4A further includes an annular cavity 7 formedin the glass or polymeric plug 1″. FIG. 1E also depicts optical vias 6in the shell 2″ which also fluidicly couple the annular saline chamberor channel 7 with the exterior which may be outside adjacent tissue. Itis anticipated that the annular channel 7 will be used to routeirrigation fluid such as saline to the ablation tip and out of theablation tip. FIG. 1E shows an irrigation fluid channel 7C coupled withthe annular channel 7 (if the plug 1″ is liquid-permeable, there may notbe a need for a localized irrigation flow channel). For simplicity,irrigation fluid channels are not shown in all the figures, but it isunderstood that the ablation tips in this disclosure can include anysuitable irrigation fluid channel(s) for routing irrigation fluid tovarious parts of the ablation tips. The irrigation fluid will, as seenin FIG. 1E, fill the annular chamber 7 and optical vias 6 therebyallowing for uninterrupted light passage along that path. The irrigationfluid will keep the ablation tip cool during ablation (i.e., less thatabout 70° C.). In this approach, the irrigation fluid such as saline orwater acts as an optical waveguide as well as a tip coolant. If theoptical via is longer than its lateral dimension (e.g., length greaterthan diameter) and is filled with an irrigation fluid such as water orsaline or an optically transmissive polymer, the filled via physicallyacts as its own light pipe along its length. In specific embodiments,the plug includes at least one channel or conduit formed on its surfaceor in its body, which serves to do at least one of the following: coupleto an optical fiber, couple to a fluid lumen, pass irrigation fluidthrough or across any portion of the ablation tip, and pass light oroptical energy through or along any portion of the tip regardless ofwhether the channel is filled with one or more of an irrigation fluid, alight conducting material such as optical epoxy or air, for example.

In the case of a product or device having only one tip-connected fiber(fiber(s) not shown in FIGS. 1A-1E), it will be apparent that in orderto have a working device, there is a need to (1) transmit and receivelight simultaneously to and from the tip along the single fiber, or (2)transmit and receive light sequentially to and from the tip along thesingle fiber. We emphasize that by single tip-connected fiber we meanthat only a single fiber is routed all the way to the ablation tip. Thisarrangement does not at all preclude a design utilizing a bifurcatedfiber, i.e., a Y-shaped fiber (single fiber which splits into twofibers) wherein the single combined transmit/receive end is in theablation tip and the dual but separate transmit and receive split endsare respectively away from the tip such as in the device handle. Thefollowing discussion addresses these two alternatives for such singlefiber-connected tip devices.

FIG. 2A is a sectional view of an optical feedback RF ablator tipillustrating an RF ablation tip having a single optical tip fiber. Notethat the tip-interior region defined by the plug comprises a singleoptical chamber.

FIG. 2B is a sectional view of an optical feedback RF ablator tipillustrating an RF ablation tip having separate tip transmit and receivefibers (two fibers). Note that the tip-interior region defined by theplug comprises two optically isolated chamber regions. While the opticalisolation is ideally 100%, it is typically a substantial opticalisolation of, for example, preferably at least about 90%, morepreferably at least about 99%, and most preferably about 100%.

In the single fiber RF tip of FIG. 2A, a catheter body 8 is connected tothe RF tip assembly 3. The catheter body 8 routes an optical fiber 9 tothe distal tip 3 from the proximal catheter control handle (not shown).The tip of FIG. 2A shows multiple optical vias or ports 5 laser drilledthrough the metallic tip shell into the tip interior glass plug orpolymer/epoxy plug. The plastic or glass optical fiber 9 is alsooptically coupled into the tip glass/polymer/epoxy plug. Because theablator has only one optical fiber 9 within the tip, fiber 9 will serveboth to emanate light 10 from the tip and to receive backscattered (orexcited fluorescent) light 11 from the tissue regardless of whether oneattempts to emit and collect light simultaneously or sequentially.

For clarity we define “simultaneous transmit and receive” to mean thatat at least one given instant there is both rightward moving emissionand leftward moving received backscattered light in the fiber(s) andthat the leftward moving received backscattered light is used to monitorthe tissue target or lesion. By the same token by “sequential transmitand receive” we mean that at at least one given instant only leftwardsbackscattered received light is moving in the fiber(s), wherein theleftwards received light was created by previously rightward movingemission light which was previously backscattered from target tissue.For either arrangement above the returning or leftwards moving lightwill contain tissue-backscattered light and possibly some undesirablereflective light from inside the tip shell 2 itself. The structure ofFIG. 2A is more prone to having some undesired tip-interior reflectionssince some light emitted from fiber 9 can reflect off the shell 2interior and go directly back into fiber 9 as “received” light. Suchtip-internal reflections reduce the signal/noise ratio for thetissue-reflected light of interest. A way to minimize such tip-interiorreflected light in the structure of FIG. 2A is to blacken the interiorof the metal shell 2 or the plug/shell interface region or provide theshell's internal surface with an antireflection coating (not shown), forexample. In the structure of FIG. 2B, we have optically isolatedtransmit and receive chambers 1 a, 1 b and their related fibers 9 a,bthus outgoing light from transmit fiber 9 a, even if some of it reflectsfrom the shell 2 interior, does not get dumped into the receive fiber 9b. Note that in the structure of FIG. 2B where the collection orreceiving fiber 9 b passes through the transmission chamber 1 a, oneneeds to provide an opaque coating 9 c to prevent dumping of outgoinglight directly into the receive path. This opaque fiber coating 9 c isin addition to the opaque barrier 1 c separating chambers 1 a and 1 b.It is noted that the opaque barrier 1 c is configured to substantiallyprevent light from traveling directly between the illumination opticalelement and the collection optical element on the order of preferably atleast about 90%, more preferably at least about 99%, and most preferablyabout 100%. The opaque barrier 1 c may be a very thin film, a thin disk,or even a metal-containing ablation member, etc.

For either of the structures of FIG. 2A and FIG. 2B, one can practicesimultaneous or sequential emission/reception. A light source forsimultaneous emission/reception simply needs to be “on” long enough thatfor a given instant one has both outgoing rightwards and incomingleftwards returning backscattered light in the single fiber device ofFIG. 2A or has rightwards light in fiber 9 a and leftwards light infiber 9 b of the dual fiber device of FIG. 2B. By the same token eitherof the structures of FIG. 2A and FIG. 2B can practice sequentialemission/reception such as for FIG. 2A wherein one would first haverightward emittable light and then, afterwards, leftward backscatteredlight in fiber 9, and for FIG. 2B wherein one would have first rightwardemittable light in fiber 9 a and then, afterwards, leftwardsbackscattered light in fiber 9 b. This sequential operation wouldrequire extremely short light emission pulses.

FIG. 2C is a sectional view of an optical feedback RF ablatorillustrating the use of metallic thin films overlying optical elements.In the ablator of FIG. 2B, the optical transmitter 1 a and receiver 1 bare contained within a metallic RF ablation shell 3 which has opticalports or vias 5 a, 5 b through which optical light passes outwards andinwards. In other words, the tip-surface real estate is shared betweenRF ablation and optical transmit/receive functions.

In FIG. 2C, the optical transmitter 13 a and receiver 13 b haveoverlying thin films 13 a′ and 13 b′ of optically transparent yetelectrically conducting metallic film instead of an overlying shell ofthe RF ablating metal electrode 3 in FIGS. 2A and 2B. This again allowsreal-estate sharing between ablation and optical transmit/receivefunctions. An example of suitable metallic films 13 a, 13 b would be ITOor indium tin oxide widely used in the display industry. FIG. 2C alsoshows a bulk, substantially solid, intermediate metallic RF ablatormember or portion 12 a. The ablator member 12 a also serves to providethe RF excitation to the transparent electrodes 13 a′ and 13 b′ therebymaking those optical elements also RF ablator members or portions. Thethin film electrodes 13 a′, 13 b′ are preferably less than about 3000angstroms in thickness, more preferably less than about 2000 angstromsin thickness, and most preferably less than about 1200 angstroms inthickness. They are substantially transparent optically, with atransparency of preferably at least about 90%, more preferably at leastabout 95%, and most preferably about 100%.

There are three basic ways of lesion formation relative to the opticalelements as illustrated in FIGS. 2D to 2F, although different variationsand combinations are possible. FIG. 2D shows the same arrangement of theoptical and ablator elements as FIG. 2B in which a lesion 16 a formsboth in front of the optical transmitter 1 a and receiver 1 b simplybecause both are also ablator portions due to their overlying RF shellor electrode material 3. In FIG. 2E, as opposed to FIG. 2D, the opticalreceiver 1 b has been taken from under the RF ablation shell orelectrode material 3 of FIG. 2D and situated separately as a receiveritem 13 b such that it now serves only an optical receive function. Thusit will be apparent in FIG. 2E that the lesion 16 a will now form onlyin front of the combined optical emitter 1 a and shell electrode 3 butnot in front of the optical receiver 13 b. If a larger lesion (than thatdepicted) is made, then eventually the lesion may also grow over theisolated receiver 13 b as well. FIG. 2F shows that both the opticaltransmitter and receiver are no longer under the electrode shell 3 butare configured as separate isolated transmitter 13 a and receiver 13 b;neither 13 a nor 13 b serve an ablation function. Instead a bulk metalRF ablator 12 a is disposed between the transmitter 13 a and receiver 13b and spaced from them. It will be apparent that the lesion 16 a of FIG.2F will form as shown in front of the ablative portion 12 a. Again, ifthe lesion gets much larger than that depicted, it may also eventuallygrow over one or both of the optical transmitter and receiver.

The light sources employable by the inventive devices may include, forexample, continuously operated arc lamps, lasers or LEDs or,alternatively, pulsed arc lamps, lasers or LEDs. By “continuous” we meanfor periods long compared to the summed optical travel time up and downthe fiber and preferably measured in seconds or longer. The readershould recognize that that guarantees that there will be both rightwardsand leftwards light occurring simultaneously. By “pulsed” we mean thelight is “on” for a period shorter than the summed up/down propagationtime mentioned above. This guarantees some light is returning after thetransmit light is stopped. The light source(s) of the inventive devicesmay be broadband (such as a halogen arc lamp) or narrowband (such as anLED or laser) or even narrowband and wavelength-scanning (such as byusing a wavelength tunable laser). The returned light for both devicesof FIGS. 2a and 2b could be detected in one or more manners such as by:(a) a wavelength scanning spectrometer, (b) a white light ormonochromatic interferometer, (c) a light sensor such as a photodiode,CCD or CMOS chip. The ingoing light may be polarized or unpolarized.Polarized returning light will also show, upon lesioning, a polarizationchange or birefringence effect. Time domain reflectometry (TDR) may beuseful for the sequential operation mode because one can discard orignore the portion of the signal not coming from the tissue itself.

The reader will be aware of the use of bifurcated fibers wherein the twosplit legs of the bifurcated end are employed for transmit and receiverespectively and the opposite single-end simultaneously (orsequentially) emits and collects light. Interferometry has the advantageof using optics to do time-gating (depth gating) faster than electroniccircuits can do so. This is how OCT or optical coherence tomographyworks. TDR uses very fast electronics to detect and characterize fiberor light-path discontinuities (which would be the tissue portion of ouroptical path) but runs out of gas on short fiber lengths because of thevery fast times. The present invention does not limit the methodology ofhow returned or received light is detected as there are several knownmethods to do so such as these; it only requires that at least somecollected light is known to have backscattered from, reflected from orotherwise passed through tissue and can be optically modified by one ormore optical interactions with the ablating or ablated tissue.

It is possible to employ a super fast picoseconds or femtoseconds laserin a pulse-echo mode to achieve the taught sequential approach, forexample. However, long pulse or continuous optical sources are generallycheaper and more compact and provide better optical signal-to-noiseperformance because of the greater numbers of photons.

Note that for the dual cavity structure of FIG. 2B, the outgoingin-tissue light comes from chamber 1 a and returning ingoingbackscattered in-tissue light enters chamber 1 b. Because these arephysically separate, optically isolated, and laterally displacedchambers or optical elements, one can operate the emission light sourcecontinuously and have virtually zero unwanted tip-internal reflectionswhich would degrade the S/N. This is a key aspect of the invention.

It will be obvious that any of the above embodiments can involvemathematically subtracting out and/or physically suppressing light whichis internally reflected within the device. Further, before lesioningstarts one can take a reference measurement of the intended targettissue and use that data as a baseline to compare to as lesioning causesreturned light changes. Normalizing each lesion's data to its prelesionbaseline is a nice way to exclude variations in light output or intissue-coupling from lesion to lesion.

Before we proceed further it is important to discuss how the changingbackscattering may be employed usefully. The term “returning light” isactually more globally correct than “backscattered” since it coverslight which is (a) emitted and received from lesioned tissue(backscattered scheme) as well as the case wherein at-least one of theemission or reception optical elements is remote from the lesion andemits (or receives) light which travels both through lesioned tissue andsurrounding or adjacent unlesioned tissue (the optical blocking scheme).

Increasing scattering also means decreasing penetration presuming onestarted with a relatively transmissive media or tissue as is typicallythe case for living human and animal cardiac tissue. If we arrange anoptical emitter and an optical receiver to both be closely situated overa forming lesion in the backscattering scheme (e.g., using the device ofFIG. 2b for example) we would expect the forming lesion in front of bothemitter and receiver to backscatter more and more light back into thereceiver as lesioning proceeds. This is indeed the actual case. However,if we provide a more distantly separated emitter and receiver (notdepicted in figures) and we form the lesion only in front of one of them(the optical blocking scheme) we would expect that as lesioning proceedswe would see less and less received or returning light because in thisarrangement the backscattering lesion is preventing light from passingthrough the lesion area due to its increasing local opacity and gettingto the more distant receiver outside the lesion region which has notopacified or made opaque. This is also indeed the observed case. So onecan see now that the up/down amplitude or intensity behavior of receivedor returned light depends on whether the lesion is formed in front ofboth, in front of just one, or in front of neither (lesion in betweenthem) of the emitter or receiver. Note in the third approach one mighteven form the lesion between the emitter and receiver wherein one alsosees a decrease in received light due to the opaque laterally blockingintervening lesion growing therebetween. Our invention only requiresthat any such change in received or returned light be monitored.

With further regard to the construction of the tip 3 in FIG. 2B, we notethat the emitting optical vias 5 a and receiving optical vias 5 b aretilted toward each other (i.e., the two sets of vias 5 a, 5 b are notparallel with each other but the emitting vias 5 a are tilted to directlight toward a tissue region and the receiving vias 5 a are tilted toreceive light from the same tissue region), thereby increasing thereturned signal amplitude and concentrating signal coming from thelesioned region only. The optical vias are typically laser-drilledthrough the shell into the plug portions. It is again emphasized that anoptical epoxy could be used to backfill such optical vias. The opticalvias preferably act to direct outgoing and incoming light, such thateach acts as a micro-miniature light pipe itself. With regard to the useof irrigation fluid such as water or saline, some or all of the vias maybe filled out with flowed irrigation fluid rather than optical epoxy. Tofacilitate fluid flow through the vias, the plug may include fluidchannels in the material or on its surface or the plug may be made of amaterial which is water-permeable. It is noted that for the device ofFIG. 2B, there may be tens or even over a hundred such vias withoutsubstantially compromising the mechanical integrity of the shell/plugsubassembly of the tip 3. This is because, unlike the mentioned priorart, our plug forms a mechanical foundation for the perforated shelleverywhere. We note that the tip of FIG. 2A is depicted as having aforward facing optical via 5 (in addition to the side looking vias 5)and that although the tip of FIG. 2B does not depict forward lookingoptical vias, it could also employ them.

We again emphasize that it is preferable, but not absolutely required,that the tip employ saline irrigant for known and appreciatedtip-cooling purposes. Such water or saline emission orifices may or maynot simultaneously serve as optical vias or conduits in our devices. Ourplug material might comprise a translucent or clear water-permeablematerial (bulk permeable) such that irrigant water can flow through itand out irrigant-only or irrigant/optical orifices. A practicaladvantage of a water permeable plug is that water inflow into irrigantorifices comes from all directions and such flows are unlikely to be allinterrupted by particulates, thrombus or clot. Also note that a waterpermeable plug material may be substantially more light-transmissiveafter it is bulk-permeated.

It appears that the use of a full emitted broadband optical spectrum maynot be required for lesion feedback and that the use of only one or afew specific wavelengths may be sufficient presuming these wavelengthsare ones known to be sensitive to lesioning. In this manner, lesionfeedback may employ one or more monochromatic sources or even one ormore wavelength-tunable sources. In that case, photo-detectors or CCDssensitive to the wavelength(s) involved may be used as light analyzersinstead of a spectrometer which is required to scan many wavelengthssuch as for looking at a broadband spectrum which has beenbackscattered. The received spectrum has amplitude versus wavelengthbehavior which is a result of both increasing backscatter with lesioningand known optical absorption lines related to in-tissue species such ashemoglobin and water.

The catheter tip according to embodiments of the present inventiondiffers from prior catheter tips that utilize a hollow cavity as theinterior emission chamber. The present tip has a glass, polymer, orepoxy plug body through which light can pass through at least one of theplug material itself, through drilled or formed optical vias or conduitsin the plug material, or through formed optical vias or conduits whichare then backfilled with saline or optical epoxy. The tip has aplurality of optical emanation and reception holes and all of theseholes do not need to be fluid emanation holes. For example an opticalvia or conduit may be filled with or occupied by moving or nonmovingsaline or nonflowing or solidified optical epoxy or plug bulk material.The via-overlying thin portion of metallic shell material would beremoved to allow light to pass. This preserves the mechanical integrityof the overall tip yet allows a considerable number of holes to achievea screen-like electrode with a significant area-percentage of opticalvias having a large total collection area. Such a screen-likeelectrode/plug can be easily electroformed, laser drilled, and cast fullof optical epoxy which also fills out the shell vias to the surface. Weinclude in our inventive scope the use of an orifice-containing metallicshell as a mask for etching or laser drilling optical vias intounderlying plug materials. Alternatively a laser can drill through botha shell and then through plug material to form such optical vias and/orirrigant vias through and into both.

According to a specific embodiment based on the features describedabove, an RF ablation catheter has a tip which both thermally ablatesand performs as an optical sensor for the ablation process involving theuse of an RF power source and associated power control circuit(s) orlogic. The ablation catheter includes a proximal control handle; acatheter lumen and body connecting the proximal handle to a distal tip;and a distal ablation tip. The ablation tip construction includes aglass or polymeric thermoformed, machined, molded or cast plug, ametallic shell enwrapping the plug, the shell being electroformed,plated or mechanically formed; at least one optical via passing throughthe shell into (or to) the plug, at least one optical fiber or conduitpassing through the lumen or catheter body to the tip plug and opticallycoupled to the plug which plug is in turn coupled to target tissues bythe tip optical vias; preferably flowed irrigant preferably passingthrough the catheter body or lumen into and out of the tip, the irrigantat least cooling the tip during or after RF ablation; a light sourcecoupled to a proximal fiber to deliver light at at least one wavelengthto the tip or a light source mounted in any portion of the catheter andcapable of delivering such light for emission from the tip; and a lightanalyzer or spectrometer coupled to a proximal fiber in order to detectchanges in at least one wavelength of returned light as lesioningproceeds, the changes in reflected, attenuated or backscattered lightcaused by the lesioning, the tissue scattered light received by theanalyzer from the tip through the one or more optical fiber(s) orconduit(s). Any irrigant orifices may or may not double as optical vias.

According to another specific embodiment based on the features describedabove, a thermal ablation catheter for ablating tissue has a tip whichboth ablates and performs as an optical monitoring or control sensor forthe ablation process involving the use of a thermal ablation powersource and associated power control circuitry or logic. The catheterincludes a proximal control handle; a catheter lumen and body connectingthe proximal handle to a distal ablation tip and containing at least oneoptical conduit or fiber; a distal thermal ablation tip comprising ametallic or metal-containing shell and an interior plug material; atleast one source of illumination whose light can be emanated from thetip into tissue adjacent the tip through one or more tip optical vias.The tip is also capable of inwardly receiving tissue-backscattered orreflected emanated light through one or more tip optical vias. Thereceived backscattered light is returned to the handle region orexternal the patient using at least one optical fiber or conduit in thecatheter lumen or body. The returned light is analyzed by one or moreinstruments for changes to one or more spectral parameters caused by thelesioning process. Again, depending on fiber arrangments discussedabove, the inherent increasing backscattering with lesioning eithercauses an increase in backscattered light when both emitter and receiveroptical vias both sit on the lesion-or cause a blocking reduction orattenuation in light received by a receiver from a more distant emitterwherein only one of those sits on the lesion. Both emitter and receivermay be off-lesion in which case the growing more-opaque in-between (oreven adjacent) lesion also acts as a blocker or as a reflector.

FIG. 3 schematically illustrates an optical feedback RF ablator withonly side-looking optical feedback. The side-looking optical feedbackpreferably spans 360 degree around the longitudinal axis 23 of thecatheter 21. In FIG. 3, an RF ablation catheter 21 includes a cathetertip which has two RF ablating portions 12 a and 12 b and two opticalelement portions 13 a and 13 b. The RF cylindrical portion 12 a formssideways lesions whereas the RF tip portion 12 b forms tip-forwardlesions. The RF ablating portions 12 a and 12 b may be constructed asmetallic shells around glass or plastic plugs similar to those shown inFIGS. 1 and 2. Alternatively, the RF ablating portions 12 a and 12 b aresolid metallic portions having channels and/or cavities to accommodatewires, irrigation fluid flow, and the like. The solid metallic portions12 a, 12 b are bonded or otherwise attached to the optical elementportions 13 a, 13 b that are made of glass, polymer, or the like (e.g.,by molding the optical element portions onto the solid metallicportions).

The optical element portion 13 a is the light emitter or transmitter.The optical element portion 13 b is the scattered light receiver. Theoptical emitter 13 a (illumination optical element) is fed light via anemission optical fiber or conduit 14 a. The optical receiver 13 b(collection optical element) returns scattered light via an opticalreception fiber or conduit 14 b. Note that some amount of light leavesemitter 13 a as light 15 a and scatters from tissue to return as light15 b to the optical receiver 13 b. This first example device onlyprovides side-looking optical feedback and not forward-looking opticalfeedback. Ablation lesions from which optical feedback can be obtainedare depicted as side regions 16 a. The emittable light arriving via theemission fiber 14 a will be broadband white light (e.g., from an arc orhalogen lamp) or will be one or more selected wavelengths (or wavelengthwindows) of light such as provided by wavelength-specific LEDs, fixedwavelength lasers or tunable lasers. The returned scattered light 15 bwill be spectroscopically analyzed (if it is broadband white light) suchas by using an Ocean Optics 2000+USB spectrometer connected to thereception fiber 14 b. Changes in the amplitudes of particularwavelengths and of whole portions of the returned scattered spectrum areknown to occur when tissue is thermally ablated and ultimately necrosed.In specific embodiments, the emitted light may include any one or moreof broadband light, broadband white light, light of a particularwavelength, light of two or more particular wavelengths, light of awavelength that can be tuned, CW (continuous wave) or pulsed light, andincoherent, coherent, or polarization-controlled light.

Before proceeding further it will be useful to mention what physicalmechanisms we have discovered which can cause backscattering (andassociated transmissive attenuation). When heating tissue above bodytemperature by any means (RF, laser, microwave, HIFU, etc.) one causesmicrobubble evolution because bodily gases such as oxygen, nitrogen andCO₂ are less soluble in warmer liquids. Such evolved bubbles areoptically highly backscattering and transmissively blocking. Acompletely different mechanism is steam bubbles wherein the temperatureis much higher and in the vicinity of 100 deg C. (at least in thebubbles). Even blood with no gas dissolved in it could form steambubbles if it approaches 100 Deg C. These steam bubbles may grow fromthe water turning to steam in the blood but may originally nucleate onthe prior above precipitating solute micro bubbles for example. Ingeneral steam bubbles are larger and get larger much faster and forciblythan the prior gas-solute reduction microbubbles. It is steam bubbleswhich create audible pops and even explosive tissue cratering in theworst cases. We have observed in our optical feedback (wherein bothemitter and receiver sit on the lesion) data that a steam pop involvesfirst a rise in backscatter and then a precipitous plunge in backscatterupon popping as a tissue flap is created. Further we have observed thateven before an actual audible pop there exist inaudible prepops whichalso involve rises and falls in backscatter. However the audible popactually appears to substantially vent itself and occurs at a point ofmaximal backscatter and shows a huge drop in backscatter upon popping.The audible pop frequently occurs after a string of 2-5 lesser inaudible(pre)pops each of which jacks up the net backscatter level more and morein a staircase fashion. Thus the point here is that the precedingnonventing inaudible pops can be optically seen to warn of an impendingventing (audible) pop such that the power can be turned down to avoidsaid audible venting pop.

Optical backscattering is also seen returning from the structure of thetissue itself as it whitens and browns during lesioning. Essentially thedenatured protein-crosslinked tissues are increasingly opaqueparticularly in the visual wavelengths as can be also seen with thenaked eye. Thus the optical technique sees BOTH microbubbling phenomenonand structural scattering phenomenon both of which act to increasebackscatter and block transmitted light.

FIG. 4 schematically illustrates an optical feedback RF ablator withboth side-looking and forward-looking optical feedback. The side-lookingoptical feedback preferably spans 360 degree. The RF ablation catheter21′ is similar to the catheter 21 of FIG. 3, but with additionalfeatures to provide forward-looking optical feedback. The transmit oremitting optical component 13 a now also has an extension 13 c extendingforward to the outer tip end-face of the RF tip portion 12 b. In thismanner, the transmit component 13 a/13 c provides emitted lightgenerally sideways as light 15 a and generally forward as light 15 c.The device of FIG. 4 retains the single optical receive element 13 bwhich is now shared between side returning light and forward returninglight. Therefore, both the sideways returning scattered light 15 b andthe forward returning scattered light 15 d will be received by thereceiving optical element 13 b. Ablation lesions from which opticalfeedback can be obtained are within the side lesioned region 16 a andthe forward lesioned region 16 b. Note that where the transmit opticalelement portion 13 c passes through the receiving optical element 13 b,the device optically masks the two light paths from each other utilizingan opaque material or film 13 ba. In specific embodiments, theillumination optical element 13 a and/or collection optical elements 13b each comprise a substantially annular optical element that opticallyemits or collects light throughout most or all of 360 degrees around thelongitudinal axis (preferably at least about 90%, more preferably atleast about 99%, and most preferably about 100% of 360 degrees of lightemission or collection.

The illumination or emission optical element and the collection orreception optical element can be made of one or more of the following: acast polymer or epoxy having optical conductance or transmissivity, aninjection molded polymer having optical conductance or transmissivity, arefractive index controlled polymer having optical conductance ortransmissivity, and a molded, machined, or ground glass material havingoptical conductance or transmissivity. The optical fibers can beoptically coupled with these optical elements by molding or casting theoptical element around the optical fiber or inserting the optical fiberinto the optical element using an optical coupling material such as anoptical epoxy or optical gel having a refractive index which maximizestransmission through the interfaces involved in the well known manner.We remind the reader that the plug material might be water permeable andif so it might achieve increased optical translucency or transparencyupon said permeation. The plug material could also be permeable andopaque (or nonpermeable and opaque) requiring all optical vias to bedrilled all the way to their respective fiber(s). This is workable butless preferred. Again we include the case wherein some or all of theoptical vias are provided by saline or water paths.

FIG. 5 schematically illustrates an optical feedback RF ablator 21″ withside-looking and forward-looking optical feedback and enhanced optics.As compared to FIG. 4, the emitting optical element 13 a/13 c isreplaced by 13 d/13 c, and the receiving optical element 13 b isreplaced by 13 e. The optical transmit or emission element portion 13 dis angled such that its outer surface casts emitted light at an anglemore tip-forward toward the RF tip portion 12 b. The optical receiveelement 13 e is shaped in a convex manner on the outer surface such thatit can collect more scattered light 15 b and 15 d from the side regionand the tip region, respectively. The optical emission element portionand optical receive element portion are shaped (or unshaped or lessshaped and index-graded such as for a GRIN lens) such that lightemission and light reception take a substantially angled departure fromthe normal or perpendicular direction with respect to the longitudinalaxis of the catheter body. This feature of shaped optical elements suchas annular lenses is somewhat similar in effect to the tilting ofoptical vias employed in the structure of FIG. 2B. These optical elementshape modifications of FIG. 5 (relative to FIG. 4) can improve thesignal-to-noise or S/N ratio of the device significantly. FIG. 5 furthershows an irrigation fluid channel 22 coupled with the emitting opticalelement 13 c which may be hollow (liquid filled) or liquid-permeable.That is, the emitting element conduit 13 c is at least partly a salineor water filled optical lumen. Of course, the ablation tip may includemultiple irrigation fluid channels having different configurations.Again receiving element 13 e is preferably shared between sideways andtip-end returning light.

At this point it is useful to mention that with an inventive catheterone would likely make either a sideways lesion or a substantiallyforward lesion, but not both simultaneously as is the case today withoutany such optical feedback. It is known that any lesioned tissue is muchmore reflective and backscattering than nonlesioned tissue for themicrobubbling and tissue-structural scattering reasons described above.Therefore, it follows that even for a shaped lens structure such as thatof FIG. 4 or FIG. 5 even if only one lesion type (side or tip lesion) isbeing formed at a given time that one will still see an appreciableincrease in scattering despite the fact that the other potential lesionarea seen by the receive lens is not being lesioned also. Again, abaseline reading taken before forming the side lesion would provide azero reference.

FIGS. 6A and 6B illustrate the optical transmit or emission elementportion of FIG. 5. FIG. 6A shows in more detail the angled transmit oremission optical element 13 d. Of particular interest is the two-partemitter element 13 d/13 c in FIG. 6B which is the dual emitter componentseen in FIG. 5. The dual (sideways and forward) emitter of FIG. 6Bpreferably is injection molded from an optical grade polymer or is castfrom an optical grade epoxy. FIGS. 6A and 6B depict opaquelight-blocking layers 13 db and 13 da which are preferably highlyreflective on the emitter element interior side. These assure thatemission light in emitter element 13 d/13 c ultimately makes it out ofthe element as emitted light 15 a even if that requires more than onelight bounce or reflection event. FIG. 6A shows an inclined surface 13dc for emitting light. FIG. 6B shows a diffusing or beam-spreading lensor numerical aperture 13 cc on the tip of the optical element 13 c foremitting light. Note that in FIG. 6B, the input optical fiber 14 adelivering light to be emitted is approximately centered on the opticalelement 13 d/13 c such that roughly half the light is emitted by theemission optical element portion 13 d as light 15 a and half by theoptical element 13 c as light 15 c. The transmit optical elements ofFIGS. 6A and 6B include the emission fiber 14 a, which is depicted ashaving a lens 14 aa on its tip inside the emission optical elementportion 13 d. The lens 14 aa may be a GRIN lens or ball lens or may besimply be a beamspreading or diffusing numerical aperture of the fibertip itself. This might be used, for example, to enhance radial lightemission or to controllably split the radial and forward emissionactivity. Such a tip lens could comprise a standalone manufactured lens,a modified fiber tip, or even a cast-in place polymeric entity. Inspecific embodiments, an additional optical component such as a mirror,prism, or lens such as a GRIN lens can be employed to more favorablycouple an optical fiber to an emitter optical element or a receiveroptical element or to more favorably distribute light to or from anemitter optical element or a receiver optical element.

FIGS. 6a and 6b depict the emitting lens structure as being a standalonecomponent. We emphasize that one or both of the emitting and collectinglenses may be molded directly to the metallic RF tip portions in a moldinstead. In that case the opaque reflective layers 13 db/13 da of FIG.6b may be replaced by the inherent opacity and reflectivity of theadjacent RF metallic tip components. Such direct molding processesassure that the reflectivity of such bonded interfaces can be predictedand relied upon to be stable.

FIG. 7 schematically illustrates an optical feedback RF ablator withside-looking and forward-looking optical feedback utilizing tip-mountedlight source(s) 17 a. The optical-feedback RF ablation catheter 21′″ issimilar to that of FIG. 5, but utilizes an in-tip or in-catheter lightsource 17 a instead of an emitting delivery fiber 14 a. The light source17 a would likely have electrical leads 17 b routed down the catheterlumen leftwards (toward the proximal end of the catheter). We note thatthe light source might be a laser, a VSCEL laser, an LED, a bulb, ahalogen lamp, or an arc lamp, for example. The light source 17 a may bewhite (broadband) or may be of a specific wavelength or wavelength rangeor might even be electrically wavelength-tunable. It may comprise awavelength tunable source or a group of sources each having a differentwavelength and grouped to deliver one or more of their outputsindividually or simultaneously to a common output path. An advantage ofthe on-board light source, particularly if fixed wavelength(s) are to beemitted, is that the catheter lumen can then contain a bigger diameterreception fiber 14 b for better sensitivity and S/N ratio.

As with irrigated catheters, the present design will preferably routeoutflowing (or less preferably recirculated) irrigation fluid such assaline through, near or past the metal shell portions of the RF tip tocool it and its contents which include the optical emitter and receiver.The near tissue-field and tip cooling which results will also thermallyprotect the optical elements, both by flowing irrigation fluid pasttheir faces and by the adjacent metallic RF parts being cooled directlyand being excellent heat sinks for the lenses. One may also choose toroute the irrigation fluid through the optical elements themselves asfor our aforementioned water-filled, water-containing orwater-comprising optical vias. For instance, the optical elements may bepermeable to the irrigation fluid such as water, saline, or the like asdescribed above, or may be composed entirely of saline or waterirrigant. Lenses might also include water lumens which simply allowwater passage through or along the lens to another location.

As discussed above, some embodiments may use saline flow paths as liquidoptical “fibers” or conduits wherein the fiber or conduit is, forexample, a) a water filled otherwise empty path, or b) a water saturatedor permeated path through a bulk permeable material which is opaque ortranslucent when saturated. This approach can even extend to making theoptical elements (emitter and receiver) comprise water containers ordefined volumes with clear walls or even with no walls on the outsidetissue-facing surfaces. In addition, the present design may save packingspace in the catheter lumen by coating/wrapping optical fibers withmetal/braid and thereby also using them as electrical power/signal/datalines.

FIG. 8 is a schematic diagram of an apparatus for RF ablation withoptical feedback. An ablation catheter 110 includes a control handle116, and an elongated catheter body 112 having a distal region 114adjacent a distal end 118. The distal region 114 includes any of theablation/feedback tips shown and described above. The catheter 110 isconnected with an energy source 120 such as an RF generator forablation, and preferably with an irrigation fluid source 124 to provideirrigation fluid. A light source 128 supplies light to the distal region118 of the catheter 110, which may be any of broadband (white, multiplewavelengths) light, laser light (single wavelength), and the like. Theexternal light source 128 is not needed if an internal light source isinstead provided within the catheter tip or handle. A light analyzer 130such as a spectrometer, interferometer, or one or more photo-detectorsof CCDs is provided for analyzing the light collected to evaluate thetissue lesioning during ablation. The light analyzer(s) 130 may includea quantification component that translates one or more measured lightparameters such as intensities or diffraction patterns into electricalsignals that can be processed with a computer and displayed graphicallyto an operator of the catheter 110. In this way, information regardingparameters of the tissue lesioning is provided to the operator and/or tothe ablation system itself to provide real time assessment of theablation and the possibility of user responsive control or automaticsystem control.

We have shown in the above figures the light analyzer(s) being externalto the catheter device and handle as in FIG. 8. As for the emitterlight-in-tip device of FIG. 7 we also include in our scope the option ofhaving a light analyzer in the catheter tip or handle. This isparticularly realistic in the case of the light analyzer beingphotodetector or CCD based as photodetectors and CCDs can be small andinexpensive.

According to a specific embodiment as described above, a thermaltissue-ablation catheter has a distal ablating tip, an intermediateextended lumen or catheter body, a proximal control handle, a source ofablation power coupled into the distal tip, and an opticallesioning-feedback subsystem. The catheter includes at least onesubstantially annular optical emitter element fed by an optical energydelivery fiber or source, the emitter emitting light into tissue forscattering therein or there from; and at least one substantially annularoptical receiver element receiving at least some of the scattered lightand feeding a returned scattered-light reception fiber or detector. Theat least one emitter and at least one receiver are spaced apart such asby an ablating tip portion or can even be adjacent one another andjuxtaposed on both outer sides by, for example, RF ablation tipportions. Emitted light will interact with a forming lesion depending onablator/emitter/receiver relative positions such that it affectsreceived light as by aforementioned increased backscattering ordecreased signal due to blocking lesion opacity. The received scatteredlight is affected with respect to an optical parameter by the lesioningaction or state of lesioning in the tissue. Such a parameter couldinclude net increases seen in reflective or backscattered amplitude atone or more wavelengths as lesioning progresses in front of anemitter/receiver pair and/or the resulting changing slopes of thespectrum in various wavelength ranges. The received light therebyundergoes changes which correlate with or can be used to qualitativelyor quantitatively estimate, measure, monitor or track lesioning progress(i.e., increased scattering and opacity). As used herein, “substantiallyannular” means that the outgoing or incoming light leaves or enters oneor more of the optical elements wherein the at least one optical elementcomprises two or more separate sub-elements distributed around thecircumference or around the 360 degree range, the optical elementthereby comprising multiple sub-elements distributed around the 360degree circumference. In one scenario wherein emitter and receiver bothface the growing lesion one correlates, during product design anddevelopment, the received light spectrums versus increasing lesion-depth(and therefore versus lesion volume), bigger and deeper lesions havingprogressively higher amplitude spectrums with changed slopes up to asaturation lesion depth. Normalization of each spectrum to itspre-lesion spectrum may also be employed. Knowing this correlation andrecording that correlation in the form of a lookup table or mathematicalrelationship, one can have the system report estimated lesion depth (andlesion volume if desired) based on the spectrum observed.

In a second scenario the lesion is formed in front of only one of theemitter or receiver and this means that light received by the receiverwill decrease as lesioning progresses because the growing lesion isblocking the lights passage between emitter and receiver.

It will be apparent that one could make a design wherein a smallergrowing lesion first decreases light and then when it is big enough tocover both emitter and receiver it increases light after that. Note thatin this approach the emitter/receiver spacing specifically indicateswhen the lesion size equals the spacing as evidenced by said change inoptical amplitude direction.

In a preferred embodiment the returned scattered light is directed to awavelength scanning spectrometer or to a specific wavelength-sensitivephotodiode. Both can sense the backscattered intensity amplitude atgiven wavelengths. The optical spectrometer analyzes returned scatteredlight in order to monitor or track one or more of: lesion progress,lesion volume, lesion depth, steam-pop potential or occurrence, presenceof char, presence of clotted blood or thrombosis, tissue proximity,angle to tissue, tissue force. Each of these phenomena causesdiscernable unique backscattered spectrum changes versus time and power.

Observed backscattering or opacification changes of the lesioning tissueare due to the increased concentration of the burned constituents of thetissue (e.g., denatured proteins), the loss of water content, theoxidation/burning of blood constituents such as hemoglobin, theformation of char, and micro bubbles which evolve or form due to tissueheating as by one or both of dissolved gas-dissolution and steamgeneration. We again stress that steam related bubbles can grow verylarge (millimeters) and can cause audible pops and the raising of thintissue-flaps if not outright cratering. We have seen again that theevolution of pop-related flaps filled with gas or liquid for at least ashort period result in a precipitous drop (after an extended rise) inbackscattered light. In all of the embodiments discussed so far thereturned backscattered light is at least some of the light which wasemitted into the tissue. Also included in our inventive scope is theadditional (or alternative) observation of optical fluorescence excitedin prelesioned and lesioned tissues by our emission light and evenobservation of radiated infrared wavelengths which constitute IRthermography. Pulsed IR fluorescence is a rapidly growing field and maybe practiced with or without fluorescent dyes introduced into the targettissues.

In the fluorescent excitation mode, the transmitted light excitesdifferent newly created (excited) returning light. That is, theoriginally transmitted returned (backscattered) light, if any, is notwhat is measured. What is measured is newly excited light that ischaracteristic of the fluorescence of certain cell types (e.g., nervecells, specific cells associated with arrhythmia, dead cells such asablated cells), or cell or blood constituents or that is characteristicof a fluorescent dye administered to the patient which preferentiallydistributes itself at similar targets of interest. Note that thetransmitted excitation light is wavelength-chosen to excite the specific(typically different) wavelength fluorescence in the known manner offluorescence microbiological imaging. Typically for fluorescence imaginga short-pulse laser is employed for illumination (e.g., femtoseconds,picoseconds, microseconds range) as this will excite the fluorescencebut be short enough not to “wash it out” by over saturation or“bleaching.” Note that this illumination is very different than long CWillumination for our above backscattering lesion feedback-and that thereturned light is new light of a likely different wavelength and alikely much lower intensity. The different wavelength makes detectioneasy since it cannot be confused with the transmitted excitation light.Since for fluorescence the light source is typically pulsed, the samefiber can be used to both transmit the fluorescence excitation pulse(s)and (subsequently) receive the excited responsive fluorescence pulse.There is a biophysical delay in the returning fluorescence pulse andthat returned pulse usually is relatively long and exponentiallydecaying. Alternatively one could fluorescence-mode transmit and receiveon separate fibers. Reduction in such fluorescence behavior coming fromdisappearing nonlesioned tissue or an increase in fluorescent behaviorassociated with increased amounts of damaged tissues accumulating such adye could, for example, be employed to track lesion progress.

The present construction has several significant advantages over priordesigns. Such advantages include:

-   a) Avoidance of optical vias which need to be optically isolated    along their via lengths, which are difficult to manufacture and    prevent optical leakage between so many tiny transmit and receive    paths;-   b) Tilted or shape-directed or GRIN-based optical orifices or vias    to increase the amount of emitted/returned signal in particular    tissue target regions such as those next to RF metallic tip    portions;-   c) Options for solid-like tip having very good structural integrity;-   d) Option for use of permeable plug material, whether itself    translucent or opaque, allowing for flow through plugs and therefore    cooled plugs/metallic shell despite the fact that the plug material    may not be an excellent thermal conductor-   e) Use of microinjection polymeric molding for lenses, resulting in    low cost and high precision;-   f) Use of molded lenses which are molded or cast directly to the    metallic RF parts;-   g) Axial separation of transmit and receive elements, thereby    minimizing returned light which hasn't scattered from tissue and    avoiding the need to optically isolate large number of transmit (or    receive) optical vias from immediately surrounding receive (or    transmit) optical chambers;-   h) Annular lenses allowing for large optical apertures without    compromising structural integrity of the tip;-   i) Use of electroforming technology-particularly where a polymeric    or glass plug serves as the mandrel, or where the electroformed    shell serves as a polymeric casting vessel;-   j) Lenses which act both sideways and forwardly (parts reduction);-   k) Ability to make the device with only two lenses (parts    reduction);-   l) Spaced lens/RF/lens sequences along axis of tip;-   m) Continuous or pulsed modes operation;-   n) Option to place one or more of light sources or reception    detectors in handle or in tip, particularly for tiny LEDS/lasers and    tiny photodetectors;-   o) Use of flowed liquid filled optical orifices which can flush away    surface bubbles, thrombus and clot; and-   p) Use of either or both of emitter/receiver/ablator element    relative positioning which causes backscattering light increases,    transmitted light decreases or both in sequence as the lesion grows    laterally or depthwise.

Finally the inventors have also noted that the optical feedback can varyas a function of tip application force and particularly how enwrapped,buried or embedded the tip becomes in the tissue upon increasing forceas more of the optical element circumference is in intimate tissuecontact. We specifically claim the use of such force-dependent opticalbehavior both as a means to estimate force for its own sake (such as toavoid dangerous tissue puncture or to assure a minimal desired load) andto account for or compensate for any variation in optical output simplybecause the force affects said output. Also included in the scope is theprovision of an independent tip force sensor to provide this forceinformation, the force sensor possibly being optical in nature andpossibly sharing one or more optical components with the lesion feedbackoptical elements/fibers and supporting hardware/software.

In the description, numerous details are set forth for purposes ofexplanation in order to provide a thorough understanding of the presentinvention. However, it will be apparent to one skilled in the art thatnot all of these specific details are required in order to practice thepresent invention. Additionally, while specific embodiments have beenillustrated and described in this specification, those of ordinary skillin the art appreciate that any arrangement that is calculated to achievethe same purpose may be substituted for the specific embodimentsdisclosed. This disclosure is intended to cover any and all adaptationsor variations of the present invention, and it is to be understood thatthe terms used in the following claims should not be construed to limitthe invention to the specific embodiments disclosed in thespecification. Rather, the scope of the invention is to be determinedentirely by the following claims, which are to be construed inaccordance with the established doctrines of claim interpretation, alongwith the full range of equivalents to which such claims are entitled.

What is claimed is:
 1. An ablation apparatus, comprising: an ablationcatheter comprising: an elongated catheter body configured for insertioninto a body of a patient and including a distal segment defining aninterior; an ablation element positioned within the distal segment ofthe catheter body; a plurality of optical emitters terminating within afirst portion of the interior of the distal segment of the catheterbody, wherein the plurality of optical emitters are configured to emitoptical radiation toward tissue in the body of the patient proximate thedistal segment; and at least one optical receiver terminating within asecond portion of the interior of the distal segment of the catheterbody, wherein the at least one optical receiver is configured to receivereturned optical radiation from the tissue, wherein the first portion ofthe interior of the distal segment of the catheter body is opticallyisolated from the second portion of the interior of the distal segmentof the catheter body.
 2. The ablation apparatus according to claim 1,further comprising a light analyzer configured to analyze the returnedoptical radiation received by the at least one optical receiver and toprovide an output indicative of lesioning occurring in the tissue. 3.The ablation apparatus according to claim 1, further comprising a lightsource configured to cause the plurality of optical emitters to emitoptical radiation in a plurality of different wavelengths.
 4. Theablation apparatus according to claim 3, wherein the light source isfurther configured to cause the plurality of optical emitters to emitoptical radiation sequentially.
 5. The ablation apparatus according toclaim 1, wherein the ablation catheter further comprises an irrigationlumen extending through the elongated catheter body and a plurality ofirrigation apertures in the distal segment.
 6. The ablation apparatusaccording to claim 5, wherein: the ablation element comprises a metallicshell over the distal segment; the metallic shell and the distal segmentdefine an irrigation cavity in fluid communication with the irrigationlumen; and the plurality of irrigation apertures are formed in themetallic shell.
 7. The ablation apparatus according to claim 1, whereinthe plurality of optical emitters and the at least one optical receiverare arranged along a longitudinal axis of the distal segment.